SYNOPTIC DESCRIPTION OF THE PHYLUM CEPHALOCHORDATA
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PHYLUM CEPHALOCHORDATA LINKS
| The following description of the phylum Cephalochordata came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984a), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), Colbert and Morales (1991), and Tudge (2000). |
- I. SYNONYMS: lancets, amphioxus.
- II. NUMBER: 23
- III. PHYLUM CHARACTERISTICS:
- A. Structure
- Symmetry: Bilateral.
- Body Cavity: Eucoelomate, enterocoelic.
- Body Covering: Covered with very thin epidermis.
- Support: Notochord.
- Digestive System: Large pharynx with many gill slits (stigmata) for filter-feeding; food trapped in mucus; food tube short and simple. Anus subterminal.
- Circulatory System: Blood system generally closed but with sinuses. Blood colorless.
- Locomotion: Fins and segmented myonemes. Active swimmer.
- Excretory System: Like protonephridia (text with tooltip) Protonephridia (protonephridium, sing.) are excretory organs that are ciliated tubules. The flame cell lies at the internal terminus ciliated tubule. but formed by peritoneum.
- Nervous System: Hollow dorsal nerve cord. Muscle fibers send processes to nerve.
- Endocrine System:
- Respiratory System Absorption through pharynx and epidermis.
- B. Reproduction:
- Reproductive System: Sexes separate; numerous gonads (text with tooltip) The term is derived from a Greek root meaning offshoot or offspring (gonos, γόνος). Gonads are sex glands in animals. Ovaries produce eggs and testis produce sperm. in paired rows. External fertilization.
- Development: Direct development.
- C. Ecology: Free-swimming benthic (text with tooltip) A benthic (adj.) organism is one that lives in or on the bottom of marine or freshwater environments. marine animals; filter-feeders.
- A. Structure
| LITERATURE CITED Barnes, R. D. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart and Wilson, Philadelphia. Barnes. R. S. K. 1984a. Kingdom Animalia. IN: R. S. K. Barnes, ed. A Synoptic Classification of Living Organisms. Sinauer Associates, Inc., Sunderland, MA. pp. 129-257. Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. 2nd Edition. Sinauer Associates. Sunderland, MA. Buchsbaum, R. 1938. Animals Without Backbones, An Introduction to the Invertebrates. The University of Chicago Press. Chicago. Colbert, E. H. and M. Morales. 1991. Evolution of the Vertebrates, A History of the Backboned Animals Through Time. WILEY-LISS, Inc. New York. Delsuc, F., H. Brinkmann, D. Chourrout, and H. Philippe. 2006. Tunicates and not cephalochordates are the closest living relatives of vertebrates. Nature. 439: 965-968. Hickman, C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company. Saint Louis. Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Company. New York. Putnam, N. H., T. Butts, D. E. K. Ferrier, R. F. Furlong, U. Hellsten, T. Kawashima, M. Robinson-Rechavi, E. Shoguchi, A. Terry, J.-K. Yu, E. Benito-Gutiérrez, I. Dubchak, J. Garcia-Fernàndez, J. J. Gibson-Brown, I. V. Grigoriev, A. C. Horton, P. J. de Jong, J. Jurka, V. V. Kapitonov, Y. Kohara, Y. Kuroki, E. Lindquist, S. Lucas, K. Osoegawa, L. A. Pennacchio, A. A. Salamov, Y. Satou, T. Sauka-Spengler, J. Schmutz, T. Shin-I, A. Toyoda, M. Bronner-Fraser, A. Fujiyama, L. Z. Holland, P. W. H. Holland, N. Satoh, and D. S. Rokhsar. 2008. The amphioxus genome and the evolution of the chordate karyotype. Nature. 453: 1064-1071. Storer, T. I. and R. L. Usinger. 1965. General Zoology. 4th edition. McGraw-Hill, Inc. New York. Tudge, C. 2000. The Variety of Life, A Survey and a Celebration of all the Creatures That Have Ever Lived. Oxford University Press. New York. |
| By Jack R. Holt and Carlos A. Iudica. Last revised: 01/26/2010 |
